Keep diving that's the thing. Try not to exceed your training too much, dive more and you'll start to relax. The anxiousness can really cause you to hoov. After awhile you'll stop worrying about the little things and calm down. Shallow dives are perfect for you to work out weighting/trim issues etc. For me getting to within a few pounds of perfect weighting helped my SAC rate dramatically! I need to lose a few pounds too but being relaxed is actually more important for air consumption. I would still think about the sunday dive group. Just tell them your experience upfront and I'm sure someone will take you along. You may have pick and choose dives until you get more experience.